ostling



Se t. v

p 1927 Y J. E. OSTLINE SERVICE OBSERVING EQUIPMENT FOR TELEPHONE SYSTEMS Original F'iled Nov. 20. 1922 6 Sheets-Sheet l Jnlm E- U'EFTZmE Sept 1927' J. E. OSTL'INE SERVICE OBSERVING EQUIPMENT FOR TELEPHONE SYSTEMS 6 Sheets-Sheet 2 Original File N V- 20. 1922 Sept. 6, 1927.

1,641,453 J. E. OSTLINE SERVICE OBSERVING EQUIPMENT FOR TELEPHONE SYSTEMS Original Filed Nov. 20. 1922 6 Sheets-Sheet ,3

%o ooo R WET-- Juhn E. Uflme Sept. 6," 1927. 1,641,453

J. E. OSTLINE SERVICE OBSERVLNG EQUIPMENT FOR TELEPHONE SYSTEMS Original Filed Nov. 20. 1922 6 Sheets-Sheet 4 mm Juhn E. Uflme kin AWuHIIII I 6 Sheets-Sheet '0 J. E. OSTLINE orlglnal Flled Nov 20 1922 SERVICE OBSERVING EQUIPMENT FOR TELEPHONE SYSTEMS \A Qua QA Sept. 6, 1927.

Sept. 6,1927

J. E. OSTLINE SERVICE OBSERVING EQUIPMENT FOR TELEPHONE SYSTEMS Original Filed NOV. 20, 1922 6 Sheets-Sheet 6 Patented Sept. 6, 1927.

UNITED STATES PATENT OFFICE.

JOHN E. OSTLINE, OF CHICAGO, ILLINOIS, ASSIGNOR. BY- MESNE ASSIGNMENTS. TO AUTOMATIC ELECTRIC INC., OF CHICAGO, ILLINOIS, A CORPORATION OF DELA- WARE.

SERVICE OBSERVING EQUIPMENT FOR TELEPHONE SYSTEMS.

Application filed November 20, 1922, Serial The present invention relates in general to traffic observation equipment for use in bserving the quality of service furnished in a telephone system, but is more partlcularly concerned with equipment of this type for use in multi-oflice automatic telephone systems; and the general object of the invention is to provide new andimproved circuit arrangements and apparatus by means of which an operator at a central zed office can observe, monitor, or supervise the service on groups of trunk lines or lines located at a plurality of outlying offices or exchanges.

A special feature of the invention is the 5 provision of means whereby trunks from any office in a multi-oifice telephone system may be automatically cut in to a centralized operators position for observation purposes, together with the provision of means for preventing two such trunks being cut in at the same time.

Another feature is an arrangement where by the numbers of the trunks of the outlying or observed offices are indicated by in 1 cheating lamps part of which are common to all observed trunks, resulting in the saving of considerable lamp equipment.

A further feature of the invention is the provision of means whereby two operators may observe traffic at the centralized office, and the provision of means for alternately distributing the trunks cut in to the two operators.

Still another feature is the provision of as auxiliary observing equipment which may bereadily connected. at any of the offices to be observed, and which, upon such connection, automatically disconnects that office from the centralized equipment.

There are other objects of the invention which have not been mentioned, but which, together with the foregoing, will be described in the detailed description which is to follow.

Referring now to the drawings, comprising Figs. 1 to 6, inclusive, Figs. 2. 3, 4i, and 5 should be placed in order with the corresponding lines at the ends thereof in alinement, and Fig. 1 should be placed above Fig. 2 with the corresponding inter-connecting lines in alinement. When 'laid out in the above manner the drawings show the complete c rcuits of a traffic observing system 'einhodyi 'in the invention. Fig 1 shows No. 601,95 Renewed November 12, 1926.

tain automatic equipment of the type usually used by a calling subscriber in extending an ordinary telephone connection. Figs. 2 and 3 taken together represent equipment which is located at an exchange to be observed, and is used for associating trunks to be observed with the central observing operator, for indicating at the observed office the number of the trunk cut in, and for controlling as sociated equipment for causing such trunk indication to also take place at the centralized oflice. Figs. 4: and 5 taken together comprise equipment located at the observing exchange, which is adapted to work in conjunction with a plurality of observed exchanges each having equipment such as shown in F igs. 2 and 3. Fig. 6 shows an operat-ors observing equipment which is adapted for use in conjunction with equipment such as shown in Figs. 2 and 3, when it is desired to concentrate the observation on the trunks of a particular exchange.

Now referring particularly to Fig. 1, the sub-station A is of the usual type, having talking, signalling, and switch controlling instrumentalities. The line switch 0 is of the well known rotary type in which the wipers have no normal position and move in a forward direction only. The line relay 112 is slow to pull up and release, as indicated by the solid black upper portion; whilethe relays throughout the drawings, having their lower portions shaded, are slow to release only. The selector D is mechanically of the usual vertical and rotary type, and accordingly its bank contacts are arranged in horizontal rows or levels. The terminal block TB is located at a point in the observed office where it is found most convenient to extend jumpers to trunks or lines to be observed. These jumpers may be fixed to the terminals of the terminal block, and may be provided with clips or the like to permit their being readily switched from one group of trunks or lines'to a other as desired. One jumper is shown in the draw ing as comprising conductors 102, 103, and,

104, and connects the trunk line extending to selector D with the first set of terminals on the terminal block TB.

Referring to Fig. 2. this shows in heavy lines the talking conductors 236 and 237 of an observation trunk, which extends through a to the central observing can.

liiU

Figs. 4 and 5. This observation trunk is common to all connecting trunks in the same office. As shown in the drawings it has been assumed that 50 isthe maximum number oi trunks which have access to the observing trunk. There will therefore be 50 connect ing trunks (such as the trunk comprising conductors 107, 108, and 109) permanently connected to sets of terminals on the terminal block TB' (Fig. 1). Each such trunk has two relays suchas 201 and 211 indi- 'vidual to it. One otthese relays is for connecting its associated trunk to the talking conductors 236 and 237, and for operating a unit trunk indicating lamp, and the other relayis for preventing such connection being made when the observation trunk is already in use, when trunks are not being observed, or when the observing equipment has been made ready to observe trunks at a time when trunks are already in use. 7

These 50 connectingtrunks with their corresponding relay sets are divided into live groups of ten each.. Each group is pxovided with one relay such as 245, and with another relay 251. In the drawing only one of the five relays 245 is shown; however, those not shown are operated over the same common conductor over which 2&5 is operated. These relays each carry ten pairs of control springs, one pair for each trunk in the 'Qi'ou'p,,-an-;l operate as a unit to control means at their associated exchange for preparing the equipment to permit trunks to be cut in. One common relay could be used for this purpose instead of live, but such a relay would be required to carry sets of contact springs, which is not thought to be desirable.

The group relays 251 to 255, inclusive, are

each provided with an operating circuit individual to the group to which they belong. These relays function to operate an associated group trunk indicating lamp, to operate an impulse sender switch controlling relay, and in addition aidin bringing about the operation of a trunk cut in signal at the observing oflice. i

The relay 2l-2is common to the observed exchange and is provided to complete the operating circuit of the relays such as 245. This relay 242 has its original operating circuit extending throughseries contacts of all out in relays of each group in the exchange. If this circuit happens to be open the relay 2&2 acts as an alarm relay, controlling the buzzer B (Fig. 3) at the observed oilice.

Relays 270, 275., 280, 226 and 257 are common to the observed exchange and function to take care of various details which will be pointed out in the detailed description which is to follow. The induction coil I is adapted to be associated with the observation trunk talking conductors 236 and 237 when the attendant is being signalledby an observing operator, and acts to inform the operator that the signal is operating. All of these The buzzer B is provided for signalling,

an attendant and may be operated either when the relay 2 12 (Fig. 2) fails to operate, or may be operated by the observing oper; ator when the attendant is desired. The key K is for use by the attendant to restart the operation oi the buzzer for a purpose which will be later pointed out.

The polar relay 376 is bridged acrossthe observing trunk conductors 236 and 237, and is adapted to'respond to each interruption of a subscribers calling device, to send ground impulses over the impulse conductors 37 9 and to operate a pen register at the observing ol'lice, the relay 371 at the same time being also maintained energized to hold open the primary winding of the repeating coil ll, to prevent excessive clicks from being produced in the observing operators re- 7 ce'iver (Fig. 5).

The switch SS is of the same mechanical construction as the line switch G of Fig. 1. This switch with its associated relays 305, 311 and 325 operates when a trunk has been cut in, to transmit series otimpulses over the combination locking and impulse trunk conductor350 to set up trunk lamp selecting svvitches at the observing oflice. The impulse series sent out by this switch are delermined by the particular bank contacts which are grounded when a trunk number is dis layed on the group andunits lamps.

' he equipment described up to this point lie is all located in one oflice. However, there locking and impulsing, and the impulsing conductors 415, 368, 350, and 352 is individual. to the No. 1 ollice and isone of ten such trunks terminatin in suitable equipment at the observing 0 cs.

New referring to Fig. 4, it will be seen that the observation trunk above mentioned terminates in springs of oilice cut in relay 401. The relay 401 is individual to the No.1 exchange. In the present case it having been assumed that there are ten offices in the sys tern there will be ten such relays, only two of which are shown. The relay 410 is assumed to be the tenth such relay, and is therefore individual to the tenth or last trunk as indicated. The relay d is common to all observed oliices. and when operated causes the observing equipment at each o'llice in the system to permit trunks to be cut in, and also prepares an operating circuit for all ofiice relays such as 401 and 410. \Vhen a trunk is cut in to the observing trunk of any oltice, the corresponding relay such as 401 will pull up to make inoperative all other ofiice relays, and to at the same time extend the observed trunk through to the observation operators equipment.

The relays 401, 410' and 405 at the .lower portion of the drawing. and their asssociated circuits, are identical to those just described. These relays have no function. as long as only one observing operator is required. However, in anticipation of future requirements a jumper block is provided, and upon original installation if only one observing position is required the solid line jumpers shown on the jumper block are all that are required. If at a future date it is desired to provide a second position, it is only necessary to connect the circuits of relays 401, are and 05 to the lower terminals of the jumper block J13, and to substitute the jumpers indicated by dotted lines for those indicated as solid lines. The conductors Y will of course extend to the No. 2 observation set which will be identical to the equipment shown in Fig. 5. WVhen the two positions are in service the relays 405 and 4.05 operate alternately to distribute the calls to the two positions.

Referring now to Fig. 5 it will be seen that the talking circuit extends via talking conductors 506 and 507 of the observation trunk to the left hand windings of the repeating coil R. and continues from the right hand windings of the same through talking key K. The key K is provided to enable the operator to switch from the high efficiency monitoring circuit to a. standard operators talking circuit, so that the operator may converse with the calling subscriber or an attendant when there trouble. The remainng keys K, K and K are for locking up the connection signalling an attendant and releasing the connection respectively. The lamps 1 and 10 shown under the heading ()llice. represent the first and tenth oflice. Since there are 10 offices in the system there will be 10 oflice lamps, for indicating oflices one to ten. The lamp 514 is a trunk cut in lamp, for indicating to the observer that a trunk is cut in to her set. The lamp 513 is provided to give the observing operator hook- Switch supervision on the calling line. The pen register PR- is operated over the conductor 437 in res )onse to im oulses sent to it by the previously mentioned polarized relay 376, (Fig. 3) and records on a tape the called number dialled by the subscriber.

The trunk lamp selecting switches T and T are of simple and well known construction, having operating magnets 515 and 532 which by means of an ordinary pawl and ratchet (not shown) move their wipers over their respective sets of bank contacts. The release magnets 530 and 534 are provided for the purpose of restoring the wiper sets to normal. The impulse series for operating these two switches are transmitted to the impulsing relay 520 by the switch SS (Fig. With the aid of relays 521 and 517 the switch T is controlled to position one of its wipers so as to engage a group lamp cor responding to the group lamp which is glow ing at the observed exchange. At the termination of the first series of impulses the relays 521 and 517 bring about the switclr ing 01 the impulse circuit to the controlling magnet ot the switch T and responsive to the second series of impulses sent out by switch SS, one of the wipers oi the switch T is positioned on a contact connected to a unit lamp corresponding to the unit lamp which is glowing in the observed ollice. Thete lamps therefore are caused to glow, to inform the observing operator the number of the trunk in use at the observed exchange.

' The equipment shown in Fig. 6 is the same as corresponding equipment shown in Fig. 5 and operates the same so far as the operator is concerned. This equipment is for use when it is desired to concentrate observation upon a particular one of the exchanges and is provided with a jack J which may be inserted in a jack J (Fig 3) of'any such exchange. An observing operator in using this equipment does not need the oilico or trunk indicating equipment shown in Fig. 5, but uses the trunk indicating equipment at the observed office. v

Having briefly described the mechanical structure of the various switches shown in the drawings, and l'ia-ving described the re la'tion ot' the various parts to the system as a whole, a detailed explanation will now be given.

The operations which take place when trunks become busy during the time the observing equipment is idle (at normal) will. first be pointed out, after which the various operations which take place when the ol serving operator prepares the equipment for receiving calls will be described.

lVhen the observing circuits are not in use the relay 245 (Fig. 2) is deenergized, and likewise all other such relays (not shown) of the remaining groups and of all other llll) oflices. When a call is initiated, for instance over the connecting trunlchaving conductors 107, 108 and 109, the private conand therefore relay 2.11 is not actuated at this time. The relay201 locks up over its armature 221 and its working contact, and through its upper winding toba-ttery. If the observation equipment is in the meantime )laced in readiness to observe callsall the relays 245 of the observed exchanges Wlll be energized. The energlzation of these relays causes the lower windin s of all re' lays 201 to be short oircuited. his does not, however, cause the deenergization of any relay 201 this relay remaining locked up through its upper winding, but acts to prevent any such relay which is not energized from energizing until a connecting trunk has been connected to the observation trunk, It will be seen therefore that the relay 201- or any other like relays which are operated will remain operated until their associated trunlr becomes idle This prevents these prior calls from interfering with calls initiated after the circuit is placed in readiness for observation.

Now referring to Fig. 5, when the operator is ready to begin work, she prepares the equipment for observation by inserting the receiver plug P into the jack J, which causes the operation of relay 405 4). This relay in turn operates to complete an operating circuit for each relay226, (Fig. 2) there being one such relay in each observed ofiice, and in addition, prepares a circuitfor all relays such as 401 and 410, there being one such relay at the observing oliice individual to each observed office. Now consider ing only the observed office shown in Figs. 1, 2 and 3. the other ofiices being the same, the operation is as follows:

The operator upon inserting the jack J into plug P completes a circuit forrelay 405, aspreviously stated. This circuit may be traced from grounded springs of jack J, conductor 502, through springs of'release key K, conductor 503, springs controlled by armature 403 of relay 401, (Fig. 4) springs controlled by ar nature 404 of relay 410, through jumper 424 on the jumper block J B, and the winding of relay 405 to battery. Relay 405 operates and at its armature 407 prepares a circuit for the pull up windings of all oliice cut in relays such as 401 and 410. Two of the ten such circuits are shown, and may be traced from battery, resistance 406, working con-tact of armature 407 and the said armae This will retare, conductor .408, to terminal 429 of the jumper blocl; J13 where the circuit divides, one branch extending by way of jumper 431 to the upper winding of relay 401, and the other branch extending by way of jumper 427 01 the jumper block to the upper'winding of relay 410. Relay 405 also closes'an operating circuit {or the common grounding relay 226. This circuit nmy be traced from the working contact of armature 411 and .the said armature, conductor 412, to terminal 428 of the jumper block JB, by way of jumper 430 to terminal 419, where the circuit divides intoas many branches as there are observed exchanges, the branch shown complete extending by way of jumper 413, springs controlled by armature 414, conductor 415, armature 316 and its resting contact, (Fig. 3) conductor 318, upper right hand winding of the repeating coil R, conductor 319, resting contact armature 320 and the said armature, conductor 322, resting contact of armature 323 and the said armature, conductor 324, through springs controlled by armature 225, and the winding of relay 22010 battery. Relay 226 energizes over this circuit, and locks up over a circuit independent of armature 323 of relay 325 (Fig. This eircuit'may be traced from the grounded conductor 322 to armature 225 and its working contact, and the windingof relay 226 to battery. Relay 226 in operating causesgroundto be applied to the common conductor 228. This circuit may be traced from grounded working contact of armature 227 and the said armature, and conductor 228, and alsocompletes a circuit for the relay 242 extending from the grounded conductor 228, conductor 229, springs controlled by armature 230, conductor 239 (which includes ei-gl'it sets of springs similar to those controlled by armature 230), springs controlled by armature 240, conductor 241, through ten similar sets of springs in each group (not shown), through the winding of relay 242 to battery. Relay 242 operates and completes a circuit for relay 245, extending from the con' mon grounded conductor- 228, armature 243 and its working contact, conductor 244, and-the winding of relay 245 to battery. Relay245 and all other such relays associated with groups 2 to 5 (not shown) energize and short circuit the. lower winding of all relays such as 201 and 210 in each. group. The observation equipment is now in readiness to observe calls.

Had the relay 242 failed to operate, (due to, a pair of spri gs such as those controlled by armature 230 beingopen) the. attendant llll tact, induction coil winding 248, conductor 349, and the buzzer B to battery. The attendant upon hearing the buzzer and noting that the trunk lamps are not glowing knows that a series contact is open; and that the same must be found and the trouble corrected before trunks in that office can be observed.

The observation set being in condition to observe calls, it will now be assumed that a subscriber at substation A (Fig. 1) initiates acall. hen the receiver is removed at substation A, a circuit is closed, over the line conductors 110 and 111 for the line relay 112 of the line switch C. Upon the energization of the line relay 112, the line switch G 0perates in the usual manner to select an idle trunk, which trunk, it Will be assumed, is the one extending to the selector D, As soon as this trunk is found, the switching relay 113 energizes at the end of the trunk selecting movement, or immediately upon the energization of line relay 112 in case the line switch was already standing upon an idle trunk, and extends the calling line through to theselector D. The line and release relays 105 and 106 of the selector D now energize in the usual manner, and the latter upon energization places ground upon the release trunk conductor 104 so as to establish the usual holding circuit for the line switch 0. As is well known, ground is maintained on the conductor 104 throughout the connection, and this is all that need be considered at this time. A circuit may now be traced from the grounded conductor 104 to the terminal block TB, conductor 109, working contact of armature 270 and the said armature, springs controlled by armature 221, and the lower winding of relay 211 to battery. The relay 211 operates and locks itself over a circuit extending from the grounded conductor 228,

conductor 229, working contact of armature 230 and the said armature, and the upper winding of relay 211 to battery. This op eration also removes ground from the portion of the loop circuit extending to relay 242. If it should so happen that more than one call was initiated at the same time, only the relay nearest the common ground would lock up, and it would cut oil the locking ground from all other such relays. Armature 231 of relay 211 in operating applies ground to the units lamp O by way of the conductor 232, causing'the units lamp 0 to glow. At armatures 234 and 285, the trunk conductors 107 and 108 are connected to the trunk conductors 236 and 237 across which is bridged the left hand, or primary winding of the repeating coil R. It will be recalled that the operation of the armature 280 disconnected ground from the loop conductor 239, which formerly maintained the relay 242 energized. Relay 242 now restores breaking the prviously traced operating circompletes an operating circuit for group re-v lay 251, and sender switch starting relay 257. This circuit may be traced from the grounded working contact of armature 222 and the said armature, conductor 233, working contact of armature 223 and the said armature, conductor 250, springs controlled by armature 224, winding of relay 251, conductor 256, and the winding of relay 257 to battery. Relays 251 and 257 both operate. Relay 251 in operating completes a holding circuit for itself, and relay 257. This circuit extends from the grounded conductor 228, conductor 229, armature 224 and its working contact, and the windings of relays 251 and 257 in series to battery. Another circuit is completed from grounded conductor 228, working contact of armature 260 of relay 251 and the said armature, and conductor 261 extending to the group lamp 0 and to battery, causing this lamp to glow. This lamp, in conjunction with the unit lamp controlled by the relay 211, indicates to an attendant at the observed office the number of trunk cut into the observation set. Relay 257 in operating, at its armature 247 breaks the previously described buzzer circuit, and at its armature 258 grounds conductor 259.

It may be well to note at this time that should the trunk made busy have been extended over the connecting trunk conductors 107, 108, and 109, resulting in the opera tion of relay 220, that the locking circuit for such relay would have extended over the conductor 239, through the various series contacts of all other relays such as the contacts controlled by armature 230 of relay 211, of the entire No. 0 group to the conductor 229, and to the common conductor 228 to ground, in which case it will be noted that the circuit would extend through nine pairs ofbreak contacts. It will be seen that if no special provision were made, should the tenth trunk of the fifth group become busy, the locking circuit for the relays, such as 211 or 220, would extend through 49 sets of contacts before reaching the common grounded oonductor 228. In the present case, this undesirable series holding circuit has been much improved by providing a shunt around all the groups of series contacts ahead of the particular group in which a trunk is cut in. This is accomplished by providing each i ii lil)

' group relay, with the exception of the-first, with an armature such as. 263, which, when operated connects the common ground conductor 228 direct to the series springs controlled by the first trunk relay of its respective group. I

Returning to the operation of the group relay 251, this relay at its armature 262 completes a circuit for office cut in relay 401 (Fig. 4). This circuit may be traced from the grounded conductor 250, working contact of armature 262 and the said armature, conductor 264, armature 364 and its resting contact, resistance 365, lower right hand Winding of repeating coil R, conductor 366, resting contact of armature 367 and the said armature, conductor 368, armature 468 and itsresting contact, to the upper Winding of relay'401 over the previously traced circuit to battery. Relay 401 operates and locks itself over a circuit extending from the grounded contact 501 of the operators jack, conductor- 502, through springs of the release key K,

conductor 503, working contact of armature at its armature 403 also removes ground from the series holding circuit of relay 405, breaking the previously prepared locking circuit for all other o'fiice cut in relays such as 401,410. If two observing trunks attempt to cut in the central observing trunk at the same time, only the relay 401 nearest the grounded conductor 503 will lock up, and it in so doing will break the initial operating circuit of all other oiiice cutin relays. The relay 405 in restoring to normal disconnects ground from all conductors such as 415 leading to the different common grounding relays such as 226 (Fig. 2). This does not, however, cause the 'deenergization of the relay 226 in the exchange in which a call has 5 moves battery from the pull'up winding of all oflice cut in relays, thereby making it impossible for a second office to be cut in. The operation of armature 450 of relay 401 causes the office indicating lamp to glow, informing the operator the ofiice in which observation is being made; armature 416 connects the impulse conductor 352 through to the pen register PR (Fig. 5) armature 417 connects the combination lock and indicating impulse conductor 350 to the impulsing relay 520 (Fig. 5) armatures' 414 and 468 connect the ofiice observing trunk to the central observing trunk extending by Way of talking conductors 506 and 507, repeatingcoils R and R and through contacts of thetalking key K V to the observers head set, permitting the operator to listen in during the progress of the call. '4 i Referring to relay 226 (Fig. 2), it will be recalled that this relay was originally enernee-1,453

gized over the upper heavy talking conductor 415 (Fig. 3). relay 40i1 4) is energized the ground formerly supplied to the above conductor by the relay 405, is cut off by the operation of armature 414 and a new holding ground coil R, conductor 505 and the winding of.

relay 504 to the grounded conductor 503.

The closure of the above described circuit in addition to holding energized the relay 226, belonging to the office under observation, causes the operation of the trunk cut in relay, which in operating causes the trunk cut in lamp 514 to glow. This acts as a guard to show the observer that a trunk is cut in to the observation set, even if the oilice lamp fails to glow, indicating that calls cannot be received from other offices or trunks, until the release hey is operated.-

The operation of the office cut in relay 401 also completed an operating circuit for the supervisory relay 536. This circuit extends from the working contact of armature 222 of relay 201' and the said armature, conductor 233, working contact of armature 223 and the said armature, conductor 250, working contact of armature 262 and the said armature, conductor 264, resting contact of armature 364 of relay 300 (Fig. and the said armature, resistance 365, lower right WVhen the office cut in loo hand winding of repeating coil R, talking V conductor 366, resting contact of armature 367 and the said armature, talking conductor 368, armature 468 and its working con tact, conductor I507, lower left hand winding of repeating coil R and the winding of the supervisory relay. 536 t o battery. This relay operates, causing the subscribers pilot lamp 513 to glow. Since the ground for operating relay 536 is supplied by the re lay 201 (Fig. 2) it will be seen that the moment the calling subscriber hangs up his receiver the relays 201 and 536 will deenergiZe causing the subscribers pilot lamp to be extinguished.

In addition to various results accomplished by the operation of relay 401, the observer is automatically listened in on the trunk over which the call is made. circuit may be traced as follows: From the observed trunk conductors 107, and 108 armatures 234, and 235 and their working contacts, conductors 236, and 237, to the left hand windings of the repeating (.oil R. From the right hand or secondary windings of repeating coil R, conductors 318 and 366, the resting contacts of armatures 316 and 367 and the said armatures, and conductors 415 and 368 to the left hand windings of This listening repeating coil R. windings of repeating coil R tothe left hand winding of repeating coil R From the right hand winding of repeating coil R through contacts of the talking key K to the operators receiver.

The "arious operations which have been described when an initiated call is cut in to the observer, all take place in close sequence when the calling party removes thereceiver from the switch-hook. Immediately thereafter, the trunk indication takes place, and usually within a few seconds the dialing of the desired number by the subscriber takes place. From this point, the observer will in the majority of cases first listen for the overflow, ringing, or busy tone; the answer of the called party; record the number dialed as indicated on the pen register tape; record the ofiice and the number of the trunk observed therein, and make any other records as required by routine. After ascertaining that the calling party has secured the party desired, and that the connection is satisfactory, the observer will place the equipment in readiness for the next call by operating the release key K. In cases where trouble or any non-standard condition is encountered, the locking, talking, signalling and tracer tone features will be brought into action. These various features as well as )thers previously mentioned will now be described.

Tmmlc indicating.

This feature is provided to enable the observer at the centralized observation point to know on which trunk the observation is being made. As in the previous description, the trunks are indicated in the observed cities by group and unit lamps. Vhen a call is cut in the relay 257 is operated over a circuit previously described, completing an initial operating circuit for the motor magnet 303 of the sending switch SS. This circuit may be traced from the grounded working contact of armature 258 and the said armature, conductor 259, through springs controlled by armature 301, resting contact of armature 302 and the said armature, and the winding of magnet 303 to bat tery. The magnet 303 operates and at its armature 304, removes a normal shunt from the winding of relay 305, which relay now energizes. The relay 305 operates and at its armature 302 breaks the operating circuit of magnet 303. magnet 303 in restoring its armatures replaces the shunt about the relay 305. and steps its wipers 306. 307, and 308, one step. A circuit may now be traced from the grounded wiper 308 and the upper 'inding of relay 325 to battery. Relay 325 operates and at its armature 301 substitutes ground from the wiper 308 for the grounded conductor 259 and keeps the rotary magnet From the right hand 303 ope 'ating, at a speed determined by the operation of relay 305. Belay 325 also locks itself up over its lower winding, by way of armature 309 and its working contact to the starting ground on conductor 259. It will be seen that the motor magnet 303 and the relay 305 will operate alternately until the wiper 308 steps off the last grounded bank contact. At armature of relay the initial energizing circuit of the relay 226 is broken, so that should this relay become deenergized by the operator operating her release key, this relay cannot again become energized while the switch SS is off normal. It will be seen that if this means were not provided and another trunkwas cut in to the observing equipment before the switch SS was restored to normal, an incorrect trunk indication would result. In the present case it has been assumed that the trunk cut in was the first trunk of the first group of the No. 1 observed exchange; therefore, as soon as the wiper 307 of the switch SS engages i s sixth bank contact, which has been previously grounded by the group relay 251, a circuit may be traced from such grounded contact, the wiper 307, springs controlled by armature 310, the winding of relay 311, and resistance 312 to battery. Relay 311 operates over this circuit and locks itself to ground, by way of the working contact of armature 310 and the said armature, working contact of arntiature 301 and the said armature, to the grounded wiper 308. The operationof armature 313 pre- 'parcs an impulse circuit which extends from the working contact of armature 304 to the working contact of armature 313 and the said armature, conductor 314:, resting con-- tact of armature 315 and the said armature, conductor 350. armature 417 and its working contact, conductor 418, through springs of the locking key K. conductor 519v and the winding of impulsing relay 520 to battery. As soon as the magnet 303 again becomes energized, a ground impulse transmitted from its grounded armature 304- and its working contact, over the above traced circuit, resulting in a. momentary energization of the impulsing relay 520. This ca the operation of slow acting relay and when the relay 520 deenergizes an impulse is repeated over a circuit extending from the grounded armature 522 and its resting con tact, armature 523 and its working contact. armature 524 and its resting contact, and the winding of magnet 515 to battery. causing the wipers 527 and 536 of switch T to be moved one step. After a short pause. the. relay 521, will deenergizc, and, in so doing, complete a circuit from grounded wiper 527 and its associated bank contact. arn'iature 516 and its resting contact. springs controlled by armature 529 and the upper winding of relay 517 to battery. Relay 517 Ell) operates and at itsarmature 524, switches the impulsing circuit from magnet 515 of the switch T" into connectionwith the magnet 532 of the switch T The relay 517 in operating also locks itself up at its armature 529, independent of the armature 516 ofthe relay 521.

Returning to the operation ofthe switch SS it will be recalled that the wipers 306, 307 and 308 were standing on their sixth bank contacts when the magnet 303 ener- .gized to send out the first impulse. When the magnet 303 deenergizes the wipers 306, 307, and 308, are stepped to their seventh bank contacts. A circuit may now be traced from the grounded bank contact 335, wiper 306, through resistance 312 to battery; This shunts battery from relay 311, causing the same to deenergize. The relay 311 restores to normal, and armature 313 disconnects the impulse conductor 314 from control of magnet 303. The next two steps taken by the switch SS are provided to allow ample time for the slow release relay 521 to deenergiZe after the first impulse or series of impulses has been transmitted to the relay 520. As soon as Wiper 307 comesinto engagement with its bank contact which is associated with the units lamp 0, relay 311 is again operated. The following energization of magnet 303 now results in the transmission of an impulse over tliepreviously traced path to the relay 520. The relay 520 is again operated, resulting in the operation of relay 521. The relay 520 now causes one impulse to be transmitted from the grounded armature 522 and its resting contact, armature 523 and its working contact, armature 524 and its working contact, and the winding of magnet 532 to battery. This causes the switch T to step its wipers 533 and 534" one step. soon as the relay 521 fallsback, a circuit for the indicating lamp 0 (Fig; 5), of the group and O of the units lamp set will glow, thereby indicating to the observer the number of the trunk under observation.

If the trunk under observation had been the tenth trunk in the fifth group, the sec- 0nd and tenth bank contacts traversed by wiper 307 would have been grounded. 'Assuming this to be the case, as soon as'wi'per 307 reaches its second bank contact, the relay 311 locked up, which perm-its themagnet 303 to transmit live impulses to the relay 520, causing the switch T to step its wipers to the fifth ban-k contact; After the fifth impulse, the deenergization of magnet 303 causes wiper 306 to again engage its grounded contact 335. The relay 311, therefore, denergizes to disconnect the impulse conductor. The next two idle steps allow suflicient time to permit the relay 521 to deenergize and to allow the switching over operation to be eflect'e'd. When the wiper 307 engages its tenth contact, the relay 311 is 9 will glow, indicating that trunk 49 is thetrunk under observation.

Dialing and number recording.

Referring now to F ig. 3, it will be recalled that the left hand winding of the repeating coil It was connected in bridge of the observed trunk by the operation of the relay. 211, by way of the conductors 236 and r 237. A polarized relay 37 6 is included in the bridge. This relay is of very high resistance, and will not in any manner effect the operation of the'line, or impulsing relay of the selector D. When a calling sub-v scriber operates his calling device to transmit the various series of impulses'corresponding to.- the called number of the desired subscriber, the short circuit-produced by the talking e'quipment'at the sub-station A removed each time the calling device springs are operated, and the polarized relay 37.6 responds to the dialimpulses, without interfering with the call in any way. It will be noted that the armature 378 of the relay 376 is grounded by the conductor 264, which conductor may be grounded by any group relay, and is at this time grounded by the group relay 251. It follows that each time the armature 378 is attracted,a ground impulse is transmitted to the pen register PR over a path extending from the conductor iii) 379, resting contact of armature 380 and the said armature, conductor 352,v armature 416 and its working contact, conductor 437, and the pen register PR to battery. It will therefore be seen that the pen register PR will record any number dialed by the calling subscriber. Another branch of the impulsing circuit just traced extends from c0nductor 379 to the winding of slow relay 371 to battery. This relay remains energized during each series of impulses, and opens at its armature 370 a point in the primary, or left hand windings of the repeating coil B. This is done to prevent unbearably loud clicks being reproduced into'the receiver of the observing operator; it does not, however, entirely prevent the clicks from being heard, permitting the operator to actually hear the dialing taking place. 7

Locking.

If, on accountof trouble or any non'stand ard condition, the observing operator desires to lock up the observed call, the locking key K is operated. This results in the operation of. the relay 280 at the observed exchange, over a circuit traced from the grounded conductor 502, springs of the signal key K springs of the locking key K, in operated position, conductor 418, working contact of armature e17 and the said armature, conductor 350, armature 315 and its resting contact, conductor 31%, armature 313 and its resting con-tact, conductor 353, and the winding of relay 280 to battery. The relay 280 in operating completes a circuit from the grounded working contact of armature 227 and the said armature, armature 283 and its working contact, and the winding of relay 275 to battery. Relay 275 operates and at its armature 286 places a 1000 ohm non-inductive resistance 288, across the condenser 372 of the repeating coil R. This places a loop across the two sides of the observed trunk, which prevents the release of any complete or partially set up connection, but does not interfere with transmission. This feature is very desirable in certain instances where it is found necessary to lock up a call during conversation.

Talking.

Whenever the observer finds it necessary to talk to a subscriber or an attendant, the talking key K will be operated. The opera tion of this key brings about the disconnection of the high efliciency monitoring cir- Signalfing.

When any non-standard condition exists where investigation is required by the observer, the call is first looked up in the manner previously described. The observing operator, after operating the talking key and conversing with the calling subscriber advising him to hang up and call a little later, will then signal the attendant at the distant exchange by operating the signalling key K When this key is operated, the previously traced circuit extending to the relay 280 is momentarily interrupted, re sulting in the transmission of a ground impulse extending from the armature 283 and its resting contact to-armature 28 i and its working contact, and the lower winding of relay 270 to battery. This relay locks up in multiple with the resistance 290 in bridge of the extended trunk conductors 236 and 237 at its armature 289, and at its armature 291 completes a circuit which may be traced from the grounded armature 282 and its working contact, working contact of armature 291 and the said armature, the primary winding 248 of induction coil 1, conductor 349, and the buzzer B to battery. This will cause the buzzer B to operate, to

signal the attendant. It should be observed that the secondary winding 293 of the induction coil I is connected in series with the resistance 290, and the winding of relay 270 which is placed across the extended trunk conductors 236 and 237 and therefore, when the buzzer is operated, a tone will be impressed upon the trunk, indicating to the observer that the attendant is being Sig-- nalled. When the attendant responds by inserting the plug P (Fig. 3) into the jack J, he also depresses the key K. The shunting effect of the attendants talking set will cause the relay 270 to release, which in turn will stop the buzzer. Conversation may now take place, and action taken to correct the non-standard condition.

Tracer tone.

After the attendant has received the observers report and ascertained the number of the trunk from the trunk indicating lamps, he will trace the connection to the point where it failed by examining in turn each of the switches involved in the connection. In order to assist him in doing this quickly and accurately, he places a tracer tone on the connection. This is the same tone as that used to indicate to the observer that the attendants call signal is being operated. However, in this case, the attendant starts it by operating the non-locking button K This will again operate the relay 270 in an obvious manner, causing it to lock itself from the trunk battery and ground in the same manner as before. The attendant will now listen in on the various switches in the built up connection without cutting out the condenser in his set. This is done by inserting plug P in the individual switch test jack (not shown) in the usual well known manner. hen he reaches the point at which he wishes to lock up the connection, be grounds the holding trunk conductor to prevent the release of the switches. He also stops the tracer tone by again short circuiting the condenser in his set, and will at the same time advise the observing operator that the trouble is found, and that the trunk can now be released from the observation set.

Release.

When the ob erver desires to release the trunk connected to the set, the release key K is operated. The operation of the key K disconnects ground from the conductors 503 and 510, causing the release of relays 504, 4:01 and 226. Relay 504 at its grounded armature 518 removes ground from the cut in lamp 514, and applies ground to the release magnets 530 and 534; of the switches T and T These magnets in turn operate and. re tore their respective Wipers to normal. As soon as wipers 527 and reach normal, the locking circuit for relay 51""? is broken and this relay releases. VVip'er 533 in restoring to normal also removes ground from the trunk indicating lamps. Relay 401 in restoring, at its armature 450 removes ground from conductor 451, causing the ofiice lamp to be extinguished. Relay 226 upon restoring, removes ground from the common. ground conductor 228. This results in the deenergization oi' the group relay 251 and trunk cut in relay 211. It the calling subscriber still has his receiver removed, the relay 201 will not restore at this time. The operator by permitting the non-locking release key K to restore to normal again completes a circuit for the operation of relay 226 identical to that previously described, thereby placing the circuit in readiness for the next call. 7

It should be noted that during the time a trunk being observed that any trunks seized will operate only their individual relay such as 210, which will lock up from battery and its two windings in series to the grounded release trunk. The operation of this relay brings about the disconnection of its corresponding cut in relay; therefore, when the relay 226 again energizes the trunks already in use cannot be cut in,thereby insuring that only initiated calls will be cutin to the observer.

4 Where large 'multi-oliice exchanges are equipped with observation equipment such as has been described, it may be found desirable to provide equipment which permits two operators to take observation at the same time. This result has been. attained by applicant, together with a novel method of distributing the trunks cut in equally between the two operators. Referring to Fig. 4, the relays 401, 410, and 405, and their associated circuits are identical to those shown in the upper halt of the drawing, and the group of conductors Y correspond to the conductors 509, 503, 507, 506, 437, 418, and 451, and extend to equipment identical to that shown in Fig. 5. Now, when it is desired to change the equipment for use from one to two positions, the jumpers such as 413, 427, 430, and 431, are replaced by the umpers indicated by the dotted lines.

New, assuming that the two operators are about to observe trunks, and further assuming that the operator whose equipment is shown in Fig. 5 is the first to insert her, plug P into the jack J, the relay 405 will operate in the manner previously described, and will, at its armature 421, open the operating circuit for the relay 405, which it will be seen can only become energized when the second operator inserts her receiver plug, and when relay 405 is deenergized. As soon as the trunk is cut in to the equipment, and the relay 405 is deenergized, the relay 405 will then operate, and in so doing permit a second trunk to be cut in. The operation of relay 405 causes battery to be applied to the common conductor 423, by way of co'nductor 420 and jumper 422. From the Common conductor 423 circuits extend through the pull up winding of each office relay 401, 410 to trunk conductors 368, 368, except the oilice relay corresponding to the trunk already in use. One such circuit may be traced from conductor 423 resting contact of armature 420 and the said armature, jumper 432, to the pull up winding of relay 410, through resting contact of armature 40S and the said armature, to the trunk conductor 368. trunk 'cut in to the No. 1 operator was extended from the No. 1 office, in which case the ethos relay 401 was operated, resulting in the disconnection of the pull up winding of the relay 401, which, like relay 401, is individual to the ex hange which hasa trunk cut in, it will be seen that the relay 401 has its pull up winding cut oil at armature 425, to prevent battery from being applied through the winding of relay 401 to conductor 368 of the busy trunk. As soon as the No. 2 operator has a trunk cut in to her set, the relay 405 will be deenergized, and providing the l lo. 1 operator is ready to observe another trunk, the relay 405 will again become energized. It will be seen that, the operation oi relays 405 and 405 takes place alternately, thereby distributing the calls to the two operators as fast as the trunks are cut 1n.

Local observation.

In the circuit arrangements previously described, where observation is taken from a central. point by one or two operators, there will be comparatively few trunks of a -parti cular oihce observed in a. givenjtime.

In certain instances, it may be desirable to concentrate observation on one exchange, so that the quality Oiservice given by that particular exchange may'be determined more accurately and in less time than would be otherwise possible. Referring now to Fig. 6, which comprises equipment identical to the corresponding equipment shown in Fig. 5. .This equipment is adapted for use with equipment shown in Figs. 2 and 3,. there being a jack J provided which is adapted to be inserted in the jack J (Fig. 3). By inserting the jack J into jack J the cut off relay 300 is operated, cutting off thetrunk extending to the centralized observing equipment. -Theope'ration of this set is identical to tiat of the centralized set in so far as the observer is concerned, except; that no ofiice and trunk indicating lamps are provided. Since observation is being taken at the same office or exchange at which the trunks are located, the trunk indicating Assumin now that the lTIO lampd at that exchange may be used by the observer.

The circuit operation differs slightly from the centralized set in that the subscribers pilot lamp 518 is controlled directly over the conductor 264. The trunk cut in lamp 514 is operated in a similar manner, from common ground conductor 228, armature 248 and its resting contact, conductor 246, armature 247 and its working contact, 0011- ductor 248 through the out in lamp to battery.

The various features of the invention having been described, and ascertained, what is considered to be new and desired to have protected by Letters Patent will be pointed out in the appended claims.

\Vhat I claim is:

1. In a telephone system, a plurality of branch exchanges, a main exchange, a plurality of trunks at each branch exchange having trunk indicating equipment associated therewith, means for making any one of said trunk lines busy, means operated when one of said trunks become busy for causing its respective number to be displayed by said trunk indicating equipment, a trunk line extending between each of said branch exchanges and said main exchange, trunk and o'liice indicating equipment associated with the main exchange, means associated with the trunk indicating equipment of the branch exchange for operating the trunk indicating equipment in the main exchange, and means operated in the main exchange for causing said office indicating equipment to be also operated.

2. In a telephone system, a plurality of branch exchanges, a plurality of trunks at each branch exchange having trunk indicating equipment associated therewith, means for making any one of said trunk lines busy, a plurality of relays operable upon a trunk becoming busy for causing the number of the busy trunk to be displayed by said in dicating equipment, a trunk line having only four conductors extending from each branch exchange to the main exchange, trunk and office indicating equipment at the latter exchange, means associated with the trunk indicating equipment of the branch exchange for causing the trunk indicating equipment in the main exchange to be operated over a single conductor of the trunk, and means at the main exchange controlled over another conductor of said trunk for causing the op eration of said oflice indicating equipment.

3. In a telephone system, a plurality of branch exchanges, a plurality of trunk lines associated with each branch, trunk indicat-- ing equipment at each branch exchange common to the trunks of that branch, means for making any one of said trunks busy, means operable when a trunk becomes busy for causing the number of the busy trunk to be indicated by said indicating equipment, said means also operable to temporarily disassociate the remaining trunks from said equip ment, a main exchange, a trunk line extending from said main exchange to each of said branch exchanges, indicating equipment at said main exchange and means at each of said branch exchanges for controlling said equipment over its associated trunk when the indicating equipment of the branch exchange has been operated.

4. In a. telephone system, a plurality of branch exchanges, trunk lines at said exchanges adapted for use by calling subscribers in extending connections, trunk number indicating and supervisory equipment common to said exchanges, common means and means individual to each of said trunks for associating the same vwith said equipment When taken for use, and means for preventing a second trunk from being associated with said equipment while the first is still associated therewith. A

5. In a telephone system, a branch exchange, a main exchange, trunk lines at said branch exchange adapted for use by calling subscribers to extend talking connections, a tratlic observing trunk connecting said branch exchange with the main exchange, means for connecting a talking trunk with said tratlic trunk when the talking trunk is taken for use, and means at the main exchange tor controlling said connecting means over the traffic trunk.

6. In a telephone system, a branch exchange, a main exchange, a trunk line in said branch exchange adapted for use by calling subscribers in extending connections, a trunk connecting said exchanges, means in said branch exchange actuated when the first trunk is seized to connect the first trunk with said last trunk, means at the main exchange operable over said last trunk for informing an observing operator thereat the number 01" the trunk in use, moans con trollable by the operator for preventing said trunk being released in case of trouble, signalling means at the branch exchange con trollable by the operator to signal an at tendant at the branch exchange, means for placing a tone on the connection for intornr ing the operator that the signal is operating, means operable when an attendant responds to stop said. signal. and tone, and means controllable by the attendant for again starting and stopping said signal and tone at will, to permit the use of said tone to aid in tracing the connection.

7. In a telephone system, a plurality of trunk lines in groups, means for making any of said trunk lines busy, a plurality of trunk indicating lamps, there being one lamp individual to each roup and ten lamps common to all groups, means responsive to the seizure of one of saidtrunks for causing particular gi'oup lamp to glow, and means also responsive to the seizure of said trunk to cause one of the common indicating lan'ips to glow to indicate the number of the trunk in use in the .ii'idicated group.

8. In a telephone system, a plurality of branch oi'iices, a main oliice, a plurality of trunks at each branch adapted for seizure by calling subscribers thereat, an observation trunk line extending from each branch to the main exchange, means at each branch responsive when a trunk is seized for connecting the seized trunk With the observation trunk xtending to the main exchange, and means at the main exchange for informing an operator when the subscriber hangs up his receiver.

9. In a telephone system, a plurality of branch offices, a main office, a plurality of triiinlis at each branch adapted for seizure by calling subscribers tnereat, a trunk line extending from each branch to the main. exchange, means at each branch responsive when. a trunk is seized for connecting the seized trunk with the trunk extending to the main exchange, and means at the main exchange responsive to such connection or signalling an observing operator.

10. In a telephone systein, branch exchanges, a plurality of trunks at each b anch, a main exchange, an obseiwnt-ion trunk extending from each branch exchi'znge and terminating in said main exchange, means for seizing any of said plurality of trunks, means responsive to the seizure tor connecting the seized trunk to the associated observation trunk, and means at the main exchange r sponsive to such connection for preventing any other seized trunk at any branch from being connected to an observation trunk.

ll. In a telephone system, a plurality of branch exchanges, a plurality of trunks adapted for seizure by calling subscribers at each branch, trunk indicating equipn'ient associated with the trunks of each branch, a central, ex hange. tratlic observing trunks extending from each branch to said central exchange. two operators positions at said centrai exchange having identical equipment for obscrvin g trailic over any of said trunks, and automatic means associated With said equipn'ient :ior alternately distributing the calls to said positions.

12. In a telephone system, a plurality of bench exchanges, a main exchange, trunk lines at each branch adapted for use by calling subscribers in extending connections, trunk indicating equipn'ient at each branch exchange for use by an attendant thereat, a traiiic observing trunk line extending from each branch to said main exchange, trunk indicating equipment at the main exchange associated with the trunk indicating equipment'ot all branch exchanges over said trat a tic observin trunk llllBS, means at the branch exchanges responsive to the seizure of a trunk for causing the trunk indication to take place at both the main and branch exchanges, an auxiliary operate-Ne tratlic observing set for use in locally observing traii'ic in any one of said branch enhan es, manually operated means for connecting the set with a branch e:-;change to be observed, and means responsive to such connection for disconnecting said branch from the main exchange observing equip-- ment.

1.3. In a service observing system, service observing equipment, service observation trunks normally disci'inneeted iironi said cquipn'ient, lines to be observed, means responsive to a call over any one/of said lines i'or connecting the S: no to an observation trunk and for connect 9; such trunirto said equipment, and automatic means for preventing any other line from being connected to the same or any other trunk While the first connected line remains connected.

it. In a service observiiig system, service observing ia'uiipment, service observation trunks normally disconnectet from said equipment, lines to be observed, means responsive to a call over any one of said lines {or connecting the same to an observation trunk and for connecting such trunk to said equipment, and means included in said equipn'ient itor rendering said connecting means effective or ineffective at the will of the observing operator.

15. In a service observing system, service observing equipment, service observation trunks normally disconnected from said equipment, lines to be observed, means responsive to a call over any one of said lines -i 'or connecting the same to an observation trunk and for connecting such trunl: to said equipment, said connecting means being normally inoperative, an qperatofs head set included in said equipment but nw-urxlly disconnected therefrom, and rsive to the connection of aid head set with said equipment for rendering said waneding means operative.

16. In a service olfrfterv'ang t in, service observing equipment located at one exchange, observation trunks extending from said exchange to other exchanges, lines in said other exchanges on which the service is to be observed, means responsive to the taking of one of said lines into use :ior connecting the same to the observation trunk extending to the exchange in which the line is located, means responsive to such connection for connecting the connected observation trunk to said equipment, and automatic means for PIQVGIliLiDg any other observation trunk from being connected to said equipment While the first connected trunk iemains connected.

1621115 FPSPOLI' lug,

17. In a service observing system, service observing equipment located at one exchange, observation trunks extending from said exchange to other exchanges, lines in said other exchanges on which the service to be observed, means responsive to the taking of one of said lines into use for connecting the same to the olricrvation trunk extend ing to the cxcl'iange in, which theiine is located, means responsive to such connection for connecting the connected observation trunk to said eipiipment, and automatic means for preventing any other line in the same exchange i'rom being coni'iected to the observation trunk which is in use.

18. In a service observing system, service observing equipment located at one exchange, observation trunks extending from said exchange to other excl'ianges, lines in said other exchanges on which the service is to be observed, means responsive to the taking of one oi said lines into use for connecting the same to the observation trunk extending to the exchange in which the line is located, means responsive to such connection for connecting the connected observation trunk to said equipment, and automatic means for preventing lines in the remainder oi? said other exchanges from being connected to the observation trunks extending to such exchanges while the first connected line remains connected.

19. In a service observing system, service observing equipment, service observation trunks normally disconnected from said equipment, lines to be observed, means responsive to a call over any one of said lines for connecting the same to an observation trunk and for connecting such trunk to said equipment, and means at both ends of the connected trunk for indicating the particular line which is connected thereto.

20. In a service observing system, service observing equipment, service observation trunks normally disconnected from said equipment, lines to be observed, means responsive to a call over any one of said lines for connecting the same to an observation trunk and for connecting such trunk to said equipment, means individual to the connected trunk for indicating th particular line which is connected thereto, and additional means common. to all said trunks for indicating such line.

21. In a service observing system, service observing equipment, service observation trunks normally disconnected from said equipment, lines to be observed, means responsive to a call over any one of said lines for connecting the same to an observation trunk and for connecting such trunk to said equipment, and means common to all said trunks but individualto said equipment for indicating the particular line which is connected to the trunk in use.

22. In a service observing system, service observing equipment located at one exchange, observation trunks extending from said exchange to other exchanges, lines in said other exchanges on which the service is to be observed, means responsive to the taking of one of said lines into use for connecting the same to the'observation trunk extending to the exchange in which the line is located, means responsive to such connection for connecting the connected observation trunl: to said equipment, and means in the said first exchange for indicating the line connected and also the exchange in which such line is located.

23. In a service observing system, service observing equipment located at one exchange, observation trunks extending from said exchange to other exchanges, lines in said other exchanges on which the service is to be observed, means responsive to the taking of one of said lines into use for con necting the same to the observation trunk extending to the exchange in which the line is located, means responsive to such connection for connecting the connected observation trunk to said equipment, a line indicating device in the exchange in Which the connected line is located, a similar indicating device in the said first exchange, an ofiice indicating device in said first exchange, and means for operating all said devices auto matically responsive to the establishment of said connections.

24. In combination, a trunk line, lines and means for separately connecting them to said trunk line, an indicator at the originating end of said trunk for indicating in any given case which of said lines connected to said trunk, a similar indicator at the distant end of said trunk, means for transn'iitting impulses over the trunk to control the distant indicator, and common apparatus for controlling the first indicator and said impulse transmitting means. 7

In combination, a trunk line, lines and means for separately connecting them to said trunk line, an indicator at the originating end oi said trunk for indicating in any given case which of said lines is connected to said trunk, a similar indicator at the distant end of said trunk, a switch for controlling the distant indicator, an impulse sender for sending impulses over the trunk to set said switch, and common apparatus for controlling said first indicator and said sender,

26. In combination, a trunk line, other lines and means for separately connecting them to said trunk line, relays selectively operated When lines are connected, an indicator controlled by said relays, an impulse sender also controlled by said relays, a switch responsive to impulses transmitted by said sender, and a second indicator controlled by said switch.

lit)

iii)

27. Line indicating apparatus comprising two groups or selectively operable relays, a sending device for transmitting two series of impulses in accordance with the setting or said relays, two switches responsive to said two series of impulses, respectively, and an indicator controlled by said switches.

Apparatus for indicating a line designation at two points simultaneously com-- prising a first set of lamps, conductors tor lightin said lan'ips, a sender devicelnchuling a point tinder having a bank connected to said conductors in multiple with said lamps, a second set of lamps and a second set of conductors, and means controlled by saidsender device tor lighting said second set of lamps over the second set 01? conductors.

,29. In aservice observing; system, a central observing station, observation trunks extending from said station to automatic exchanges, each of said automatic exchanges havingtrunk lines adapted to be seized and released under the control oi the subscribers, means responsive to the seizure of a trunk line in one of said exchanges for connecting the trunk line to the observation trunk extending to such .excl'iange, and

means controlled from said central 3 n or preventing the subscriber calling from releasing the seized trunk line.

30. In service observing system, a central observing station, observation trunks extending from said station to automatic exchanges, each of said automatic exchanges having; trunk lines adapted to be seized and released 1 lder the control. of the Slll'JSClllJQI'f, means responsive to the seizure ot a trunk line in one of said exchanges for connecting the trunk line to the observation trunk extending to such exchange, and means coutroiled from raid ce itral station for connecting a conductive bridge across, the seized trunk line to prevent the calling subscriber from releasing the same.

31. In a service observing system, two exchanges, an observation trunk connecting said exchanges, means for connecting said trunk with a line in one exchange over which a connection is being set up, means under control of an operator at the second exchange for preventing the release oi such. connection after it is set up, a signal at the '"irstex mange controlled bv said operator to notify an attendant at the first exchange that connection has been locked up, and means for automatically transmitting a signalling current back over the said observation trunk to the operator to notify her that the said first signal is being operated.

32. In a service observing system, an observation trunk, relays for connecting lines to said trunk one end thereof, Said relays ing nerm y inop r tiv a c mm e ay for rendering said relays operative, a circuit for said common relay including serially related contacts on all. said connecting relays, means for closing said circuit, and means automatically responsive to give an alarm in case one of said serially related contacts is open when the said circuit closing means is actuated,

33. In a nulticfiice telephone system, an observation set at one oflice, observation trunks extending from such oflice to the other offices, means responsive to a call at one of the other ofiices for connecting the calling line to the observation trunk extend ing to the oiiice concerned, and means responsive to such connection for connecting the observation trunk to said observation set.

34. In a telephone system, a plurality of branch exchanges, a plurality of trunks ateach branch exchange, a main exchange, atrunk line having only four conductors extending from each branch to the main ex change, trunk and oflice indicating equipment at the main exchange, means at the branch exchange operable when one of said trunks becomes busy for causing the trunk indicating equipment to be operated over a single conductor of the trunk to the main exchange, and means controlled over another conductor of said main exchange trunk for causing the operation of said ofiice indieating equipment.

85. In a telephone system, a plurality of branch exchanges, a plurality of trunks associated with each branch exchange, a main exchange, an observation trunk extending from said main exchange to each of said branch exchanges, means operable when one of said trunks in one of said branch exchange becomes busy for causing the busy trunk to be connected with the observation trunk extending to such branch exchange, said means also operable to temporarily disassociate all the remaining branch exchange trunks from said observation trunks, indicating equipment at said main exchange, and means at each branch exchange for controlling said equipment over its associated observation trunk when a busy branch exchange trunk is connected with its associated observation trunk.

36. In a telephone system, abranch ex with the said last trunk, means at the main exchange operable over said last trunk for i i-forming an observing operator thereat the number of the trunk in use, means cont-rola e by t Qper e f r p e ent n said trunk being released in case ottroub'le, and 

